Method of placing gas sensors on drones to benefit from thrust air flow via placement and scoops

ABSTRACT

A multirotor drone comprises a main body and an air channel embedded within the main body having an air inlet on the surface of the main body, multiple propellers that induce an air flow toward the air inlet and into the air channel, a microcontroller positioned and configured to control navigation of the drone by actuation of the plurality of propellers, an air scoop having a section positioned at the outer surface of the main body adjacent to the air inlet which is adjustable so as to capture and divert air into the air inlet and air channel or to block air flow into the air inlet, and a gas sensor positioned within the air channel. The air scoop is positioned to capture air flow from at least one of the plurality of propellers into the air channel and to the gas sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application relates to two other patent applicationsentitled, “Improved Gas Sensing for Fixed Wing Drones using Scoops” and“Calibration Methods for Gas Sensors Mounted In-Stream of DronePropeller Airflow,” respectively, which are being filed concurrentlywith the present disclosure.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to methods and apparatus forenhancing air flow to gas sensors incorporated in drones, improvingtheir sensitivity and accuracy. More particularly, the disclosurerelates to a drone and a method for increasing air flow to a gas sensordisposed in an embedded air channel using adjustable air scoops.

BACKGROUND OF THE DISCLOSURE

Drones can be usefully applied to monitoring tasks such as detection ofhazardous particulates and gases as they can autonomously travel todesired locations, such as industrial facilities, at which monitoring isdesired. Such drones can be equipped with detectors and sensors thatenable the drones to detect gasses at very low concentrations. Thesensors generate data which can be transmitted electronically to a droneoperator or other station. The data can provide useful indicators. Forinstance, the data can concern current plant conditions and safety.Safety monitoring is particularly relevant in oil and gas installationshaving environments with corrosive and/or flammable gases. Even at lowconcentrations, such hazardous gas can represent risk of explosion orother safety accidents, and, at a minimum, provide importantinspection-related information.

Drones have typically been equipped with gas sensors by appending thesensors from booms or fixtures supported by the body or wings of thedrone. However, appending the gas sensors in this external manner canleave the drone sensors exposed to uneven and uncontrollable air flowwhich distorts the detection profile and which can reduce detectionsensitivity. In particular, the external sensor placements do notharness the capabilities of the drone flight characteristics to increasegas detection sensitivity.

SUMMARY OF THE DISCLOSURE

The present disclosure provides a multirotor drone that comprises a mainbody having an outer surface, and an air channel embedded within themain body having an upstream end at an air inlet at the outer surface ofthe main body, a plurality of propellers coupled to the outer surface ofthe main body, wherein actuation of at least one of the plurality ofpropellers induces an air flow directed toward the air inlet and intothe air channel, a microcontroller positioned within the main bodyconfigured to control navigation of the drone by actuation of theplurality of propellers, an air scoop having a section positioned at theouter surface of the main body adjacent to the air inlet, the air scoopbeing adjustable between a first position to capture and divert air intothe air inlet and thereby to the air channel and a second position toblock air flow into the air inlet, and a gas sensor positioned withinthe air channel. The air scoop is positioned to receive and capture airflow of at least one of the plurality of propellers to induce the airflow into the air channel and toward the gas sensor.

In certain embodiments, the microcontroller controls the position of theair scoop via an actuator to optimize air flow into the air channel andto the gas sensor.

In certain embodiments, the multirotor drone further comprises acompression spring coupled to the main body and to the air scoop andoperative to provide a biasing force against the scoop closing over theair inlet completely, and a drag flap coupled to the air scoop externalto the surface of the main body, wherein the drag flap imparts arotational moment to the air scoop which tends to close the air scoopover the air inlet when exposed to air flow above a prescribedmagnitude.

The multirotor drone can also include at least two legs and respectiveretraction shafts into which the at least two legs retract, the legsbeing configured to retract into the respective retraction shafts inresponse to contact with a surface upon landing. The air scoop cancomprise first and second arms, the first arm positioned adjacent atleast one of the retraction shafts and mounted for pivotable motion inresponse to retraction of the respective leg into the adjacentretraction shaft during a landing, and the second arm being positionedadjacent to the air inlet and arranged to pivot outwardly to expose theair inlet as the first arm pivots during the landing.

In certain implementations, at least one of the propellers is pivotableto a position in which air flow generated by the propeller is directednormally toward the air inlet and the air channel to increase air flowtoward the gas sensor.

The air inlet and the air scoop can be positioned so as to receive airflow from at least two propellers of the multirotor drone.

In certain embodiments, the multirotor drone further comprises at leastone additional sensor configured to detect a reference gas.

In another aspect, the present disclosure also provides a method forincreasing air flow to a gas sensor of a multirotor drone having a mainbody and a plurality of propellers. The method comprises arranging thegas sensor within an air channel embedded inside the main body of thedrone, the air channel having an opening at a surface of the main body,mounting an adjustable air scoop adjacent to the air inlet. The airscoop is adjustable to be selectively positioned to receive air flowgenerated by at least one of the plurality of propellers to direct airflow into the air channel and toward the gas sensor.

In certain embodiments, the drone further comprises an actuator coupledto the air scoop, and the method further comprises the step of activelycontrolling the air scoop using a microcontroller via the actuator.

In certain embodiments, the method further comprises biasing the airscoop in and open position over the air inlet, and providing a dragflap, exposed to the air flow provided by the at least one propeller,the drag flag being coupled to the air scoop and configured to force theair scoop toward a closed position against the biasing force in responseto an air flow from the propeller above a prescribed magnitude.

In other embodiments, the method further comprises mechanically couplingthe air scoop to landing gear of the multirotor drone such that, uponlanding, retraction of the landing gear causes the air scoop to pivotinto an open position.

In some implementations, the method further comprises adjusting at leastone of the plurality of propellers into an orientation which induces airflow in a normal direction toward the air inlet. An additional propelleroriented to direct air flow in a normal direction toward the air inletcan also be provided.

These and other aspects, features, and advantages can be appreciatedfrom the following description of certain embodiments of the inventionand the accompanying drawing figures and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary multirotor drone having anair scoop for a gas sensor according to an embodiment of the presentdisclosure.

FIG. 2 is a schematic block diagram of a drone electronic control systemaccording to one embodiment of the present disclosure.

FIG. 3 is a schematic side and partial cut-away view showing anembodiment of an air scoop of a multirotor drone according to thepresent disclosure.

FIG. 4 is a schematic view of an embodiment of an air scoop mechanismaccording to the present disclosure.

FIG. 5 is a schematic diagram illustrating another embodiment of apassive air scoop mechanism according to the present disclosure.

FIG. 6 is a perspective view of an exemplary fixed wing drone having anair scoop for a gas sensor according to an embodiment of the presentdisclosure.

FIG. 7A is a schematic view of an embodiment of an air scoop mechanismfor a fixed wing drone according to the present disclosure.

FIG. 7B is a schematic view of another embodiment of an air scoopmechanism for a drone according to the present disclosure.

FIG. 7C is a schematic view of a further embodiment of an air scoopmechanism for a drone according to the present disclosure.

FIG. 8 is a flow chart of an embodiment of the reference gas method forcalibrating a gas sensor of a drone according to the present disclosure.

FIG. 9 is a flow chart of an embodiment of another method forcalibrating a gas sensor of a drone according to the present disclosure.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE DISCLOSURE

The present disclosure provides mechanisms for increasing andcontrolling air flow to gas sensors embedded in multirotor or in fixedwing drones by providing air scoops which capture propelled air flowinto an air channel containing a target gas sensor. In multirotordrones, the propelled air flow is provided by positioning the air scoopwithin range of the air flow generated by one or more of the propellersof the drone. In fixed wing drones, the propelled air flow is providedby the flight speed of the drone itself, which causes an entrained airflow. The increased air flow to the gas sensor improves the sensitivityof the gas sensor and provides a more consistent profile of gasconcentration as compared to prior art designs which employ exteriorlypositioned gas sensors, such as on booms or other fixtures. In one ormore of the embodiments described herein, the air channel can provide aninterior shape which increases the volume of ambient air that is sampledduring a given period of time. In such embodiments, the interior shapeof the air channel can comprise a Venturi chamber in which there is aconstriction downstream of the air inlet and ahead of an air outlet. Thegas sensor can be positioned within the Venturi chamber either upstreamor downstream of the constriction. As the gas sensor can experiencedrift and air flow characteristics which can vary, it is also importantto calibrate the gas sensor. The present disclosure thus also providesseveral methods for calibrating gas sensors embedded in drones.

Sensitivity Enhancements for Multirotor Drone

Multirotor drones use a plurality of spinning-blade propellers toachieve flight, maneuverability, and stability. Typical models use fourpropellers (quadrotor) or six propellers (hexarotors). The drones comein a larger number of sizes and form factors which are classified asfollows: “large” drones are between 25 kg and 150 kg in weight, “small”drones weigh between 2 kg and 25 kg, and “micro” drones weigh 2 kg orless. Many prevalent models are small or micro-drones.

FIG. 1 is a perspective view of an exemplary quadrotor micro drone 100.The drone depicted is one of the Phantom models (Phantom 4) manufacturedby Shenzhen DJI Sciences and Technologies Ltd., of Shenzhen, China. ThePhantom 4 drone is about 1.4 kg and can reach flight speeds of 44 mph.It is understood that the specific drone size and form factor shown inFIG. 1 is merely exemplary, and the principles of the present disclosurecan apply to any drone designs and sizes subject to the conditionsdiscussed below.

The drone 100 comprises a main body 110 that houses electrical andelectronic components that are used to operate the drone. In theexemplary drone 100, the body is somewhat pillow-shaped with a widemidsection narrowing toward the periphery. Arranged at each of thecorners of the top of body 110 are rotary motors 115 a, 115 b, 115 c,115 d. Propeller rotors 120 a, 120 b, 120 c, 120 d are positioned on andcoupled to each of the respective motors 115 a, 115 b, 115 c, 155 d.Diagonally opposite motors 115 a/115 c and 115 b/115 d create rotationin the same direction (clockwise or counterclockwise) while the firstand second pairs create rotation in the opposite direction from eachother to complement each other. Motors 115 a-d are operable to rotatethe propellers 120 a-d at selected speeds between 0 and 8000 RPM.Landing gear 125 is attached to the bottom side of the drone body 110(opposite from the top side on which the propellers are positioned). Thelanding gear 125 can include a pair of flexible “legs” as shown whichallow the drone to stably land on a surface. Also attached to the dronebody 110 is an antenna 130 used to transmit and receive signals in alicensed communication band (typically the WiFi band, but other bandsare possible). A payload fixture 135 is also coupled to the bottom ofthe drone body. The payload fixture 135 can be used to installadditional equipment to the drone. Common examples of payload equipmentinclude cameras, and Lidar sensors for monitoring purposes, storagecontainers for storing environmental samples, and grippers and mountsfor package delivery, among others. Other components such as LEDindicator lights (not shown in FIG. 2) are also commonly attached to thesurface of the main drone body 110.

The components of drone 100 discussed thus far are typical components ofknown drones. The present disclosure modifies existing drones byproviding an air inlet 140 and air scoop 142 to provide air flow to aninternal gas sensor. The air scoop is positioned at the outer surface ofthe main body adjacent to the air inlet. More particularly, the airscoop is positioned to receive and capture air flow of at least one ofthe plurality of propellers. This positioning along the outer surface ofthe main body induces air flow toward the air inlet, into the airchannel, and toward the gas sensor. In one embodiment, the air scoopcomprises a flap, shutter or similar structure that has a first positionto capture and divert air into air inlet 140 when in an “open” position,and to block air flow into the air inlet 140 when in a second, “closed”position. It is intended, however, that the air scoop be adjustable to aposition in between the fully open and fully closed positions to providea moderated air flow to the gas sensor. When the air scoop 142 is in anopen position air flow from at least one of the plurality of propellersis induced or otherwise directed toward the air inlet 140 and flows intoan internal air channel 145 (shown in dashed outline) leading to the gassensor (not shown). As will be appreciated, the air channel can have anair outlet (not shown) to ensure a continuous flow of air therethrough,with the aperture at the outlet sized to meet aerodynamic constraintssuch as to minimize turbulence in air flow. In propeller-based drones,the air channel 145 is advantageously embedded within the main body ofthe drone. The air channel has an upstream end at the air inlet of theair scoop 142. It opens at the outer surface of the main body. In thisor other embodiments, the air channel 145 has an interior shape whichincreases the volume of ambient air that is sampled during a givenperiod of time, for instance, comprises a Venturi chamber.

As described below, the scoop can be actively (i.e., electronically)controlled or passively controlled. When actively controlled, amicrocontroller, such as the microcontroller 210 discussed next or aseparate controller configured by code executing therein, providessignals to a solenoid or other device to move the air scoop between itsfirst and second positions and anywhere in between. In certainembodiments, the position to which the microcontroller moves the airscoop can be variable as a function of the volume of air being directedinto the air inlet or as a function of the volume of air impinging uponthe gas sensor within the air channel 145.

The inlet to the air scoop is dimensioned to be large enough to obtainsufficient incoming air flow to permit for efficient trace gasdetection, but small enough to not interfere with the aerodynamics ofthe drone flight. In some implementations, the inlet has a crosssectional area of between 5 cm² and 1.5 cm². Further details regardingembodiments of the air scoop are discussed further below.

FIG. 2 is a schematic diagram showing the electronic control systemhoused inside the body 110 of the drone. The drone electronic controlsystem 200 includes a microcontroller 210, sometimes referred to as aflight controller, that can have advanced capability. Examplemicrocontrollers that are specifically adapted for drones, and whichhave low latency, include Reduced Instruction Set Computer (RISC) chipsets such as e ARM®Cortex®-M7 32-bit RISC core which is rated at a speedof 216 MHz. Microcontroller 210 also encompasses cache memory andfirmware that can be added to perform or optimize specific functions.The microcontroller 210 accesses and executes program modules andalgorithms stored in memory unit 220 or local cache memory included inthe microcontroller. Among the program modules most pertinent to thisdisclosure are a navigation module 225 (which can include a number ofsubmodules), a user interface module 230, and an air scoop controlmodule 235. (The modules are shown in a box with dash outline toindicate that they are not hardware components themselves, but ratherare stored in the memory unit 220).

The microcontroller 210 is also coupled to a communication unit 240 anda suite of sensors 250, which can include a inertial measurement unit252, a global position system transceiver 254, an accelerometer 256 andone or more target gas sensors 260 (referred to herein in the singularas “gas sensor,” with no loss of generality intended). As noted above,the gas sensor is positioned in an air channel (e.g., air channel 145)that is exposed to the ambient environment via an air inlet on thesurface of the main body of the drone. All of the components abovereceive power, directly or indirectly (i.e., through one or moreintermediate components) from a power supply unit 270. In most drones,the power supply unit 270 comprises a chemical battery such as a lithiumcell, but the battery unit 270 can also comprise solar cells, or a fuelcell (particularly in large drones).

The navigation module 225 includes program instructions forconfigurating the microcontroller 210 to execute a flight plan for thedrone according to commands delivered in real time by an operator (e.g.,via a mobile device), or according to a preprogrammed route. In eithercase, the navigation module determines how the microcontroller 210activates the propeller motors 280 of the drone to accomplish a numberof flight maneuvers such as, but not limited to, climbing, hovering, anddescending in the vertical plane, as well as movements in the horizontalplane control by increasing or decreasing propeller speed of some of thepropellers relative to others. The navigation module 225 also controlsthe pitch, roll and yaw of the drone as part of the navigation control.The user interface module 230 includes program instructions forconfiguring the microcontroller to interface with a drone controllerapplication running on the operator device. For implementations in whichhuman operators pilot the drone, the user interface module 230 processescommands received from the operator device for drone flight direction.

In accordance with a salient aspect of one aspect of the presentdisclosure, the air scoop control module 235 includes programinstructions for configuring the microcontroller 210 to operate (e.g.,open or close) the air scoop 142 to enable air capture air into the airchannel 145 to reach the gas sensor 260, or otherwise, to moderate orprevent air flow into the air channel. When the microcontroller 210executes the instructions of the air scoop module 235, themicrocontroller determines the next adjustment to the position of thescoop (via an actuator mechanism that responds to electrical signals),and the timing thereof, based on a number of calculated factorsincluding, but not limited to, drone body speed, individual propellerspeed, gas sensor sensitivity, air mass flow, etc. to provide thegreatest amount of air flow to the gas sensors consistent with propellerthrust and/or lift. In other words, there can be trade-off between gassensor sensitivity and thrust/lift which can be accounted for in theprogrammed instructions utilized by the air scoop control module 235. Assuch, when gas sensor measurements are considered a high priority, themicrocontroller can modify commands delivered to the navigation modulebased on input from the air scoop control module in order to increase orreduce air flow, depending on the circumstance, to provide an optimalair flow to the gas sensor.

In other embodiments, the air scoop is deployed passively, meaning thatthe scoop opens or shuts depending upon forces acting upon it, ratherthan by electronic commands delivered by the microcontroller. In oneembodiment, the force acting to open or maintain the scoop in an openstate is inversely proportional to propeller thrust. In suchembodiments, it can be helpful to reduce full propeller thrust duringair gas measurements. FIG. 3 is a schematic view of an embodiment of anair scoop mechanism according to the present disclosure. As shown, mainbody of the drone 310 includes air inlet 315, air scoop 320 and airchannel 325. The air channel can have an air outlet (not shown) toensure a continuous flow of air therethrough, with the aperture at theoutlet sized to meet aerodynamic constraints such as to minimizeturbulence in air flow. The air scoop 320 is a lever-like structure thathas a front section 322 that extends over the drone body and isdimensioned to be able to cover the air inlet 315 when positioned flushagainst the main body of the drone. A rear section of the air scoop 323is coupled to a drag flap 324. A compression spring 328 is positionedbetween the front section of the air scoop 320 and the drone body 310.The compression spring is coupled to the main body and to the air scoopand is operative to provide a biasing force against the scoop closingover the air inlet completely. In such embodiments, the compressionspring biases the front section in an “open” position and againstshutting flush against the drone body. A gas sensor 330 is positioneddownstream (in the direction of air flow) within the air channel 325inside the main body 310 of the drone. In some implementations, the gassensor 330 can be positioned 2 to 6 cm within the air channel 325, asmeasured from the air inlet 315, to achieve more laminar airflows, tominimize mechanical oscillations, to minimize other forces that can beexperienced by the gas sensor, or in view of a combination of theseconsiderations. In addition, additional sensors (not shown) can beincluded in the air channel for calibration purposes as discussed below.A propeller 340 is shown to the right, with lines emanating from thepropeller indicating the force of air flow generated by the propeller340. As shown, the air channel is oriented largely tangential to thedirection of the air flow stream generated by propeller 340 but receivesat least a portion of the air flow which enters the channel. The frontsection 322 of the air scoop is positioned directly in the air flow andis deployed to divert a portion of the air flow from the propeller intothe air channel 325. In this or other embodiments, the air channel 325has an interior shape which increases the volume of ambient air that issampled during a given period of time, for instance, comprises a Venturichamber. As will be appreciated, the air channel can have an air outlet(not shown) to ensure a continuous flow of air therethrough, with theaperture at the outlet sized to meet aerodynamic constraints such as tominimize turbulence in air flow.

As FIG. 3 illustrates, a moderate force of air flow generated bypropeller generates a rotational moment on the front section 322 of theair scoop, acting in a counterclockwise direction away from the springtoward a more “open” position. The compression spring adds a force inthe same direction. Conversely, at high air flow speeds, namely thoseabove a prescribed magnitude, there is a countervailing rotationalmoment on the drag flap 324 which acts in a clockwise direction Theclockwise moment on the drag flap 324 is transmitted to the rear section323 of the air scoop which acts to move the front section 322 clockwiseagainst the force of the compression spring 328, reducing the exposedarea of the air inlet 315. In some embodiments, the drag flap 324 issignificantly larger than the air scoop. For example, the drag flap istwice the size of the air scoop in one embodiment. Such an arrangementhas the drag flap providing a stronger force than the counteractingforces of the air scoop and spring 328. This maintains the air channelclosed. For example, at hovering speeds, the air flow can be high enoughfor forces on the drag flap 324 to close the front section of air scoop322 over the air inlet. Whereas, after landing, the air flow provided bythe propellers is low enough to keep the air scoop open, while stillproviding sufficient air flow to the gas sensor. Alternatively, the sizeand angle of the drag flap 324 and front section of the air scoop 322,and the stiffness of the spring 328 can each be selected to ensure thatthe air scoop is partially open at hovering speeds, closed at activeflight speed, and fully open when the drone is landed. The angle of thedrag flap provides moderation of the open/closed relationship of the airscoop by decreasing the amount of airflow it is in contact with as itcloses, which provides an additional control over the air scoop inregard to it opening partially.

One of the objectives of this mechanism is to provide a moderated,stable air flow and pressure in all types of flight conditions, that issufficient for the gas sensor to make sensitive measurements but is notso great as to potentially damage the gas sensors due to overly flowspeed or pressure above the prescribed magnitude. The mechanism alsohelps in reducing the range of calibration required, as it acts as apassive control feature that reduces the range of possible air flows andpressures. More generally, the spring can be arranged to keep the scoopat least partially open against antagonistic forces provided by the draglevers at the back of the scoops, which tend to close the scoops athigher air speeds.

The air scoop mechanism shown in FIG. 3 can be deployed mid-flight inorder to increase detection in specific times or areas or can bedeployed during a landing while the propellers are still in operation.The propelled air flow into the air scoop increases gas detection in aspecific area. The microcontroller 210 or other controller can beconfigured by code executing therein to make adjustments to the airscoop position as a function of air flow from the propeller being abovea prescribed value stored in the memory unit 220.

Alternatively, passive control of the air scoop can be based on magneticforces. The propellers can be made from or include conductive materialsthat create a magnetic field while they are spinning, in proportion totheir speed. The air scoop can be designed to open or close at athreshold average propeller speed.

FIG. 4 is a schematic view of another embodiment of an air scoopmechanism according to the present disclosure. The mechanism illustratesin FIG. 4 is adapted to be deployed when the drone lands upon surface.Drone 400 includes a main body 410, an air channel 415 positioned at theside of the main body, landing gear including retractable legs 417, 419and propellers 425, 427. A gas sensor 430 is positioned in the airchannel 415. The air channel can have a particular shape to increase thevolume of ambient air that is sampled during a given period of time, forinstance, a Venturi chamber shape. The air channel also can have an airoutlet (not shown) to ensure a continuous flow of air therethrough, withthe aperture at the outlet sized to meet aerodynamic constraints such asto minimize turbulence in air flow. The main body 410 also includesretraction shafts 431, 433 into which the landing gear legs 417, 419retract into the respective retraction shafts in response to with asurface upon landing. An air scoop 440 is positioned on a side of themain body 410. The air scoop 440 comprises several segments. In theillustrated embodiment, the segments are L-shaped. More generally,however, the air scoop 440 has an upper segment 442 and a lower segment444 positioned in, and pivotable within, a hollow channel within thedrone (the channel is not explicitly shown in the view of FIG. 4)coupled to retraction shaft 431. The upper segment 442 is biased by aspring 445 to stay in position flush against the side of the main bodyin the absence of a counteracting force. The lower segment 444 has atleast a section positioned within retraction shaft 431. In operation,upon landing, leg 417 is forced upwards and enters retraction shaft 431and impinges upon the lower segment 444 of the air scoop. The forciblecontact of landing gear leg 417 on lower segment 444 causes the airscoop as a whole (both segments 442, 444) to pivot counterclockwiseagainst the biasing force of the spring coupled to the upper segment442. In other words, the lower segment 444 pivots in response to theretraction of the leg 417, causing movement of the upper segment 442against the biasing spring or any other element which normally retainsthe air scoop in a position which closes or reduces air flow into theair channel 415. More generally, the present disclosure also envisionsother mechanisms to translate the normal forces transmitted upon landinginto a force that opens an air scoop. Importantly, the mechanismoperates to open the scoop which propeller 425 (at least) is inoperation so that the air flow into the scoop, and to the gas sensortherein, is increased.

FIG. 5 is a schematic diagram illustrating another embodiment of apassive air scoop mechanism according to the present disclosure. Drone500 includes main body 510 and propellers 515, 517 coupled to horizontaledges on the top of the main body. One side of the main body includes anair channel 520 having an inlet at a surface of the main body whichchannel contains a gas sensor 530. In this embodiment, propeller 515, onthe same side of the main body as the air channel, can be freely pivotedat least ninety degrees. The propeller 515 can thereby pivot from anormal flight position in which propeller 515 is positioned over the topof the main body, to a “perpendicular” position ninety degreescounterclockwise at the side the main body. In the perpendicularposition, air flow generated by propeller 515 is oriented normally tothe face of the air inlet and is directed into the air channel 520.While only one propeller 515 is shown pivoted in FIG. 5, in someembodiments, other propellers can also be pivoted to provide air flowdirectly to the air channel 520. The embodiment depicted in FIG. 5 hasthe advantage that the pivoted propeller can provide air flow while thedrone is not in flight. As will be understood, the aperture of the airchannel 520 can be at other orientations and the pivoting of thepropeller 515 need only be sufficient to adjusts from a first,flight-position suitable for navigating the drone 500 to anair-channeling position when the drone is stationary (i.e., afterlanding) in order to increase air flow into the air channel 520 andtoward the gas sensor 530. As will be understood, the air channel 520can have an interior shape which increases the volume of ambient airthat is sampled during a given period of time, for instance, comprises aVenturi chamber. Also, as will be appreciated, the air channel can havean air outlet (not shown) to ensure a continuous flow of airtherethrough, with the aperture at the outlet sized to meet aerodynamicconstraints such as to minimize turbulence in air flow. In embodimentsin which the propeller pivots to provide airflow into the air channel520 and toward the gas sensor 530, the air channel is preferably on afront surface of the drone as taken in the direction that the drone isnormally flown in order to catch air and passively couple it into theair channel as the drone moves in the normal direction during flight.

In a related embodiment to that shown FIG. 5, in which one or morepropellers are activated while the drone has landed is substantiallystationary, the gas sensor can be placed on the external surface of thedrone body rather than in a channel embedded in the main body of thedrone. The gas sensor can be placed on the surface indicated by thedirection in which the drone is usually flown to capture air flow.

Enhancements for Fixed Wing Drones

While the embodiments discussed above pertain to multirotor drones,aspects of the present disclosure also apply to fixed wing drones. Anexemplary fixed wing drone is illustrated in FIG. 6. The fixed wingdrone (FW drone) 600 comprises a main fuselage body 610, wings 615, 620which extend from lateral sides of the fuselage body 610, frontpropellers 622, 624 and rear propeller 627, among other components. Inaccordance with another salient aspect of the disclosure, an air inlet630 and air scoop 640 are shown on the wing 620. In an alternativearrangement, the air inlet and air scoop can be on the central fuselage.In either case, the inlet is in fluid communication with an embedded airchannel. As will be appreciated, the air channel can have an air outlet670 (see FIG. 7) to ensure a continuous flow of air therethrough, withthe aperture at the outlet sized to meet aerodynamic constraints such asto minimize turbulence in air flow. It is noted that the size of theinlet and scoop are enlarged for illustrated purposes and are not shownto scale.

As will also be appreciated, the notion of a FW drone 650 can comprise atailless construction, the so-called “flying wing” variety, as opposedto the version illustrated in the figures. Such a construction includesan aircraft body having the outer surface referred to above with the airinlet 630 and air scoop 640, and the air channel embedded within theaircraft body. The body and wing are integral, for instance, as in theNorthrop B-2 stealth bomber.

The FW drone 650 includes an electronic control system, similar to thatshown in FIG. 2 and described above, with the difference that thenavigation module will be configured differently by the executing codebecause the flight characteristics of the FW drones differ from those ofmultirotor drones. The control system can be mounted within either thefuselage or at least one of the wings. FIG. 7A shows an embodiment of anair scoop mechanism which can be incorporated on either the fuselagebody 610 or wings 615, 617 of the FW drone 600. The air scoop mechanismcan be positioned on the front or rear of either component, with dueconsideration given to aerodynamic factors specific to each drone designthat can cause certain positions for the air scoop to be moreadvantageous than others. The air scoop mechanism shown in FIG. 7A issimilar to the air scoop mechanism shown in FIG. 3, discussed above, butdoes not rely upon the direct air flow generated by a propeller. Themechanism includes an air channel 660 embedded in the fuselage 610 thatis exposed to the environment via the air inlet 630. However, air scoop640 which comprises an adjustable, pivotable flap, shutter or similarstructure that, depending upon its position, is provided to selectivelyblock or open the air inlet 630 to the air channel 660. The air flowinto the air channel can be changed or impeded altogether by the airflap, thus allowing the drone to minimize exposure of its onboard gassensor until the drone has reached an area of interest where gassampling is required. Additionally, by avoiding the scooping of air whensensing is not needed, drag is reduced which is helpful to preservepower for longer flights.

In the embodiment shown, the air scoop 640 comprises a front section 642which extends outwardly and is dimension to cover the air inlet 630, anda rear section 644 which either extends to or is coupled to a drag flap645. The front section is biased to against closing by a spring 649. Asillustrated, the spring 649 is a compression spring. The air scoop 640and drag flap 645 are provided and function similarly the embodimentshown in FIG. 3 to moderate air flow into the air channel 660. In someembodiments, the gas sensor 650 can be positioned 3 to 6 cm within theair channel 660 as measured from the air inlet 630 to ensure sufficientair flow without undue exposure to the force of the air flow at the gassensor. The air scoop 640 can be actively (electronically) or passivelycontrolled. A compression spring (not shown in FIG. 6) can be includedto bias the air scoop 640 toward an open or closed position, dependingon the embodiment.

The forward flight of the FW drone 600 tends to enhance air flow intothe air inlet 630. Forced air is channeled past the gas sensor in such away as to increase air flow or pressure. This, in turn, increases thevolume of ambient air that is sampled during a given period of time. Airflow to the gas sensor via the air channel can be increased, reduced, orstopped depending on changes in the position of the air scoop 640. Theair scoop has a section which is positioned adjacent the inlet to theair channel. The air scoop is adjustable between a first position inwhich air is captured during forward flight of the drone and divertedinto the air inlet and, thereby, to the air channel, and a secondposition to block air flow into the air inlet.

The air scoop can be configured in different ways in various embodimentsconsistent with the present disclosure. Thus, for instance, in FIG. 7B,an air scoop 670 is embodied as a L-shaped air channel having two airchannel arms 672, 674 connected at an elbow. In some implementations,the entire air channel is embedded inside the drone wing or body.Alternatively, part of air channel arm 672 can extend outwardly from thesurface of the drone wing or body. As the drone flies through the air,air passes into an inlet and through the first air channel arm 672 ofthe scoop. The perpendicular air channel arm 674 is gated by a valve 675coupled to a compression spring 678, illustrated schematically, thatbiases the valve 675 to be in an open position. A gas sensor (not shown)is positioned downstream of the valve, that is, it is further away fromthe inlet and the air channel arm 672. The valve can be T-shaped, asshown, having a bearing surface (e.g., the crossbar if T-shaped). Thevalve has a component that is exposed to air flow. In operation, as ifthe drone reaches a threshold air speed, the force of the air flowpresses down on the crossbar or other bearing surface of the valve 675,tending to close the valve and reduce or completely prevent air flowthrough the perpendicular air channel arm 674, thus acting to passivelycontrol the airflow past the gas sensor.

FIG. 7C illustrates another embodiment for controlling air flow to a gassensor of a drone. During flight, the airfoil shape of the wings offixed wing drones can create an air pressure differential between thetop and bottom of the wings, as is a known principle which enablesairplanes to fly. This principle can be used as a mechanism to controlair flow to a gas sensor.

Thus, as shown in FIG. 7C, a wing includes an embedded air channel 680oriented longitudinally through the wing. A valve 682 is positionedwithin the air channel. A pressure sensitive linking element 685 iscoupled to the valve. In some embodiments, the linking element ispositioned near the top of the wing. The linking element 685 isconstructed so as to respond to the pressure differential between thetop and bottom of the wing during flight. The pressure differentiallifts the linking element 685, which in turn pulls the valve 682 toblock and reduce air flow through the air channel 680. In someembodiments, a biasing spring (not shown) is positioned to bias thevalve to return to an open position. A mechanical stop can also becoupled to the valve to limit upward motion of the valve 682. Thelinking element 685 can be coupled to the valve in such manner that themotion of the valve is amplified in comparison to the linkage motion dueto the pressure differential. In certain embodiments, the linkingelement 685 can be positioned distally at a different location of thewing from the valve.

In some embodiments, the air scoop module is configured to activelycontrol the air scoop to close in order to reduce drag when the drone isnot in an area requiring gas detection, or when the air flow to the gassensor does not require enhancement, such as when improved measurementsensitivity is not needed. The air scoop module can be configured toopen the air scoops further when a trace amount of a target gas isdetected in order to improve measurement sensitivity. Conversely, theair scoop module can also be configured to close the scoop when a highconcentration of corrosive or explosive gas is detected as part of anabort procedure to minimize interaction between exposed electronics(e.g., of the gas sensor) potentially explosive or damaging atmosphere.More generally, the active control algorithm executed by the air scoopmodule via code within the processor implementing that control schemecan be configured as a closed-loop control technique which seeks tomaintain an approximately constant pressure/flow rate through thechannel using gas sensors in the channel, sensors out of the channel(e.g. on the wings), and/or flight controls to predict and intelligentlyadjust the scoop to maintain one or more specific airflow conditions.Closed-loop circuits of this type can respond dynamically to changessuch as through a feedback circuit to maintain the parameter that isbeing controlled to remain within a prescribed tolerance, such as, withonly a prescribed amount of change in pressure, flow rate, or both.

Drones can also be equipped with additional structures to ensure thatflight characteristics of the drone are not deleteriously affected bythe air scoop control. For example, since use of a single air scoop cancreate an asymmetrical drag force on the drone—depending on the positionof the air scoop, in some embodiments, the drone can be equipped withadditional air scoops that are controlled (actively or passively) toopen symmetrically relative to the drone, the direction of flight, orboth. In an alternative embodiment, other structures positioned on thedrone or drone surfaces (e.g., flaps) can be either dynamically adjustedby the microcontroller or be designed to operate to compensate for theimpact of the air scoop on the flight characteristics of the drone.

In active control implementations, a microcontroller can be configuredbe code executing therein to control the air scoop to open or closerelative to flight speed to moderate the amount of air flow to the gassensor at any given time, and at any given speed. Relatively constantair flow and pressure improves the accuracy of the gas sensormeasurements as well as the need for extensive calibration across alarge range of flight speeds, and in certain embodiments themicrocontroller is configured to execute a control sequence thatrepositions the air scoop during flight to generally maintain a constantair flow and pressure at the gas sensor. The microcontroller controlalgorithm can incorporate additional factors such as the sensitivitycharacteristics of the gas sensor. Additionally or alternatively, themicrocontroller can be configured to control the air scoop to open onlywhen gas detection is desired, such as when the drone has reached adesired geophysical location, and can be moved toward a closed positionto reduce drag by reducing the degree of air scooping when a sufficientvolume of air is being diverted.

In passive control implementations, the air scoop can be designed toopen only below a threshold flight speed, or in a variable manner basedon flight speed to maintain a relatively constant quantity (flow andpressure) of air passing into the air channel and past the sensors. Thelatter can be accomplished using the counteracting force of thecompression spring which tends to keep the air scoop in a pivoted, openposition, in combination with the drag flap 680 which serves to at leastpartially close down the air channel at higher flight speeds.

Drone Gas Sensor Calibration

Gas sensors can have variable characteristics and their measurements canbe affected by operation of the drone via factors such as air speed andpressure. Calibration is therefore required to ensure that the gassensor used in the drone accurately measures ambient gas concentration.By increasing the air flow, pressure, or turbulence across a gas sensor,one can increase the rate of diffusion of molecules of interest into theactive components of the sensor, increase the quantity of thosemolecules that come in contact with the active components of the sensor,or both. Regardless, this enables smaller concentrations of molecules inthe ambient environment to be detected than would otherwise be possible.The increased air flow, pressure or turbulence therefore acts as a formof magnification for the gas sensor. This enhances the sensitivity ofthe sensor, enabling not only the detection of lower concentrations ofthe molecule of interest, but also the ability to obtain increasedtime-sensitivity in measurements of changes in concentration of atargeted gas molecule as the effective resolution increases. Another wayof looking at this is to realize that enhanced air flow past the sensoreffectively increases the volume of gas sampled in a given time period.

The present disclosure provides embodiments of methods for calibratingthe gas sensors used in drones described above. In general, and aproposto each of the embodiments disclosed herein, the gas sensors provide asignal that must be converted to a concentration of gas measured fromthe ambient environment as collected through the air channels describedherein.

A first method of calibration according to the present disclosureemploys using one or more additional sensors that are used to detect theconcentration of one or more gases that have a concentration known witha substantial degree of accuracy. The additional sensors are termed“reference sensors” and the gases of presumed known concentration areterm “reference gases”. A reference gas can be, for example, oxygen,carbon dioxide, nitrogen, etc. These gases are atmospheric gases whichhave a known concentration and variance (for example with regard toaltitude). In the calibration method, referred to as the reference gasmethod, at least two gas sensors are employed, one gas sensor,represented by those discussed above, detects a target gas. Eachadditional sensor detects a reference gas. Importantly, both the targetgas sensor and the reference gas sensor are arranged to experienceidentical air flow from propeller flow (multirotor embodiments) orflight speed (fixed wing embodiments and multirotor drones, in somecases). This can be accomplished, for example, by placing each of thesensors at a similar depth within the air channels and/or in acircumferential arrangement around a radially symmetric channel. Thetarget sensor can then be calibrated based on the measurements of thereference sensor.

A two-dimensional grid of calibration coefficients can be created over amapping of ranges of air speed and pressure. As noted, more than onereference sensor can be employed. Additional reference sensors canincrease accuracy at the cost of extra design complexity (ensuring thatall gas sensors receive similar air flow) and cost. Similarly,additional target gas sensors can be employed as well with sameconsiderations of improved accuracy versus design costs. Furthermore, asan additional check, external measurements of reference gas can be madeusing environmental sensors outside of the drone, spectroscopy orsensors on the drone that are mounted outside of the air stream producedby the propellers or forward drone flight to ensure the referenceremains constant.

FIG. 8 is a flow chart of an embodiment of the reference gas calibrationmethod according to the present disclosure. The method begins in step700. In step 705 measurements of a reference gas are taken by areference gas sensor positioned to receive propeller air flow inmultirotor drones or on a wing or body to experience flight-induced airflow in fixed wing drones. In step 710, the reference gas concentrationis compared with an expected reference gas concentration. On the basisof this comparison, in step 715 a correction factor is determined whichequalizes the measured and expected values. In step 720, the target gasis measured using a gas sensor experiencing the same air flow as thereference gas sensor. In step 725, the measured target gas concentrationis calibrated using the correction factor applied to the reference gasmeasurement. The method ends in step 730.

A second method calibrates the target gas sensor based on detectedcharacteristics of the air flow including mass air flow rate, pressureand or temperature (air flow calibration method). According to thismethod, the drone is equipped with addition sensors that can determineone or more of air flow rate and air pressure and, in someimplementations temperature as well. In certain embodiments, if the airchannel is configured as a Venturi chamber, air flow rate or pressurecan be calculated in a conventional manner based on the air flow throughthat structure. At a preliminary gas sensor rating stage, concentrationmeasurements are made of sample of known concentration at baselinevalues of air flow, pressure, and temperature. Additional measurementsat the same known concentrations but with different air flow andpressure are performed. The additional measurements provide “deltas”indicating changes in concentration measurements solely due to thechange in air flow characteristics. At this point, the behavior of thegas sensor measurements in response to air flow parameters is determinedand can be used by a suitably programmed processor to perform thecalibration. In some implementations, the variation can be stored as atable in memory of the electronic control system. Alternatively, thebaseline gas sensor measurements can be modified based on a physicalmodel of how variation in air flow, pressure and temperature effect thebaseline values. For example, if measured air flow is higher than thebaseline value, this would indicate a greater throughput of air to thegas sensor compared to the baseline which can yield a misleadingly highconcentration reading. Thus, even though one of the main purposes of thepresent disclosure is to provide such enhanced air flow to the drone gassensors, calibration can require the removal of at least some of theeffects of enhanced flow on concentration measurements.

FIG. 9 is a flow chart of an embodiment of the air flow calibrationmethod according to the present disclosure. The method begins in step800. In step 805, propelled air flow rate is detected; in step 810,ambient pressure is detected; and in step 815, temperature is detected.It is noted that in some embodiments, step 815 is excluded. Steps 805,810, 815 can be performed simultaneously or in different order. In step820, the gas sensor makes a measurement of the concentration of thetarget gas. In step 830, the gas sensor measurement is modified based onthe detected air flow, pressure, and temperature. The method ends instep 835.

Another calibration method employs a dynamic equilibrium sensor incombination with a reference gas sensor. In this embodiment, unlike thefirst embodiment above, the calibration is automatic, and it is notnecessary to apply a correction factor. The dynamic equilibrium sensorcomprises a reference gas sensor, a membrane positioned downstream fromthe reference gas sensor that exhibits an equilibrium binding affinitybased on the relative concentrations of the target and reference gases,and an additional sensor that detects the relative concentrations of thetarget and reference gases. The dynamic equilibrium sensor outputs asignal (e.g., optical, electrical that is an indicator of the relativepartial pressures of the two gases and is independent of air flow orpressure conditions. As the reference gas concentration is known andsubstantially constant, the target gas concentration can be determinedbased on the output of the dynamic equilibrium sensor. As one example, asensor that binds to hydrogen sulfide at a rate of ten times that ratethat the sensor binds to oxygen outputs a constant signal based onrelative concentrations of the two gasses that is independent ofpressure or air flow.

While calibration is generally required to ensure accuracy of the targetgas sensor, in some applications, such as detection of particularlyhazardous gases, precise gas concentration is not of interest so much asthe presence of the target gas in any magnitude. Drones can be used tomonitor various locations for the presence of hazardous target gases andthe control systems can be configured to generate an alarm notificationupon positive detection. In such applications, the control systemon-board the drone can be configured to respond to any positive sensingby the gas sensor of a specific chemical in any concentration. Theresponse can be to abort the drone's mission, shutting down the systembeing observed, and so on. Sensitive gas sensors can be utilized forspecial-purpose (that is, specific gas constituent sensing) to support abinary response: everything is fine, or everything must stop. Such aconfiguration, as noted, can proceed without calibration.

It is to be understood that any structural and functional detailsdisclosed herein are not to be interpreted as limiting the systems andmethods, but rather are provided as a representative embodiment and/orarrangement for teaching one skilled in the art one or more ways toimplement the methods.

It is to be further understood that like numerals in the drawingsrepresent like elements through the several figures, and that not allcomponents or steps described and illustrated with reference to thefigures are required for all embodiments or arrangements.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises” and“comprising”, when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, or components,but do not preclude the presence or addition of one or more otherfeatures, integers, steps, operations, elements, components, or groupsthereof.

Terms of orientation are used herein merely for purposes of conventionand referencing and are not to be construed as limiting. However, it isrecognized these terms could be used with reference to a viewer.Accordingly, no limitations are implied or to be inferred.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

The subject matter described above is provided by way of illustrationonly and should not be construed as limiting. Various modifications andchanges can be made to the subject matter described herein withoutfollowing the example embodiments and applications illustrated anddescribed, and without departing from the true spirit and scope of theinvention encompassed by the present disclosure, which is defined by theset of recitations in the following claims and by structures andfunctions or steps which are equivalent to these recitations.

What is claimed is:
 1. A multirotor drone, comprising: a main bodyhaving an outer surface, and an air channel embedded within the mainbody having an upstream end at an air inlet at the outer surface of themain body; a plurality of propellers coupled to the outer surface of themain body, wherein actuation of at least one of the plurality ofpropellers induces an air flow directed toward the air inlet and intothe air channel; a microcontroller positioned within the main bodyconfigured to control navigation of the drone by actuation of theplurality of propellers; an air scoop having a section positioned at theouter surface of the main body adjacent to the air inlet, the air scoopbeing adjustable between a first position to capture and divert air intothe air inlet and thereby to the air channel and a second position toblock air flow into the air inlet; and a gas sensor positioned withinthe air channel; wherein the air scoop is positioned to receive andcapture air flow of at least one of the plurality of propellers toinduce the air flow into the air channel and toward the gas sensor. 2.The multirotor drone of claim 1, wherein the microcontroller controlsthe position of the air scoop via an actuator to optimize air flow intothe air channel and to the gas sensor.
 3. The multirotor drone of claim1, further comprising: a compression spring coupled to the main body andto the air scoop and operative to provide a biasing force against thescoop closing over the air inlet completely; and a drag flap coupled tothe air scoop external to the surface of the main body, wherein the dragflap imparts a rotational moment to the air scoop which tends to closethe air scoop over the air inlet when exposed to air flow above aprescribed magnitude.
 4. The multirotor drone of claim 1, furthercomprising: landing gear including at least two legs and respectiveretraction shafts into which the at least two legs retract, the legsbeing configured to retract into the respective retraction shafts inresponse to contact with a surface upon landing; wherein the air scoopcomprises first and second arms, the first arm positioned adjacent atleast one of the retraction shafts and mounted for pivotable motion inresponse to retraction of the respective leg into the adjacentretraction shaft during a landing, and the second arm being positionedadjacent to the air inlet and arranged to pivot outwardly to expose theair inlet as the first arm pivots during the landing.
 5. The multirotordrone of claim 1, wherein at least one of the propellers is pivotable toa position in which air flow generated by the propeller is directednormally toward the air inlet and the air channel to increase air flowtoward the gas sensor.
 6. The multirotor drone of claim 1, wherein theair inlet and the air scoop are positioned so as to receive air flowfrom at least two propellers of the multirotor drone.
 7. The multirotordrone of claim 1, further comprising at least one additional sensorconfigured to detect a reference gas.
 8. A method for increasing airflow to a gas sensor of a multirotor drone having a main body and aplurality of propellers, comprising: arranging the gas sensor within anair channel embedded inside the main body of the drone, the air channelhaving an opening at a surface of the main body; mounting an adjustableair scoop adjacent to the air inlet, wherein the air scoop is adjustableto be selectively positioned to receive air flow generated by at leastone of the plurality of propellers to direct air flow into the airchannel and toward the gas sensor.
 9. The method of claim 8, wherein thedrone further comprises an actuator coupled to the air scoop, andwherein the method further comprises the step of actively controllingthe air scoop using a microcontroller via the actuator.
 10. The methodof claim 8, further comprising: biasing the air scoop in and openposition over the air inlet; and providing a drag flap, exposed to theair flow provided by the at least one propeller, the drag flag beingcoupled to the air scoop and configured to force the air scoop toward aclosed position against the biasing force in response to an air flowfrom the propeller above a prescribed magnitude.
 11. The method of claim8, further comprising mechanically coupling the air scoop to landinggear of the multirotor drone such that, upon landing, retraction of thelanding gear causes the air scoop to pivot into an open position. 12.The method of claim 8, further comprising adjusting at least one of theplurality of propellers into an orientation which induces air flow in anormal direction toward the air inlet.
 13. The method of claim 8,further comprising providing an additional propeller oriented to directair flow in a normal direction toward the air inlet.